Bicycle frame



June 9, 1936. G. s. LEWIS BICYCLE FRAME Filed Aug 9, 1934 Patented June9, 1936 UNITED STATES BICYCLE FRAME George S. Lewis, Evanston, Ill.,assignor to Battery Patents Corporation, Chicago, 111., a corporation ofIllinois Application August 9,

6 Claims.

This invention relates to a bicycle frame and more particularly to aframe for a girls bicycle.

An object of the invention is to provide a novel brace-frameconstruction which is' simple but which greatly increases the strengthof the frame without adding any substantial weight or bulk.

A further object is to provide a lightweight frame consisting ofcastings and tubes secured together without welding and without bolts,screws and other like devices. Other specific objects and advantageswill appear as the specification proceeds.

The invention is illustrated in a preferred embodiment, by theaccompanying drawing, in which Fig. l is a side View in elevation of aframe embodying my invention; and Fig. 2, a broken plan view of thesame.

In the illustration given, A designates a head casting; B, a clustercasting; C, a hanger casting; and D, a brace-casting. V

The head casting A is preferably formed of a light metal such asduralumin or other light and sturdy aluminum alloy. Preferably, thecasting is designed to provide a streamline structure providing at itsfront a tubular part I 0 adapted to receive the steering shaft and witha rearwardly extending tube ll bifurcated at i2. Also, the casting isprovided with a tube It which is bifurcated at I4.

The cluster casting B is provided with a main body portion 15 providingtherethrough a central bore adapted to receive the vertical tube IS. Thecluster casting B is preferably formed of the same material used incasting A and is provided at its rear side with an integral rearwardlyextending fork portion ll bifurcated at l8.

The hanger casting C is provided with a central horizontal aperturereceiving the bearing IQ for the crank. The casting is provided with atubular extension 2! directed toward the head casting A and with atubular extension 2! receiving the lower end of tube It. integrallyformed with casting C is a rearwardly projecting extension 22 which isbifurcated at 23. Each of the forks of the bifurcated portion of castingC is provided with heads 2Q as in the usual bicycle frame construction.

In the manufacture of bicycle frames for girls bicycles, where the topbar or tube is eliminated, I have found that severe strain has beenplaced upon the vertical tube connecting the cluster casting to thehanger casting, and also upon the upper tube extending from the headcasting.

1934, Serial No. 739,158

After some use, there is a tendency for the vertical tube to bend underthe strain. In most cases where the frame has broken down, I havediscovered that the yielding occurred in the vertical tube or in theconnection leading from the head casting to the vertical tube. In orderto overcome such defects, without, at the same time, adding to theweight of the structure in any substantial degree, I have provided abracecasting D which is provided centrally with a tubular collar portion25 receiving tube It and with a downwardly turned brace-arm 26bifurcated so as to provide flanges 21 straddling the top portion of theextension 22. A pin 28 may be passed through the flanges 21 and theextension 22 to hold the arm 26 against rattling, etc. At its forwardside, the casting D is provided with a curved extension 29 bifurcated at3B and receiving the end of tube 3!. The tube 3| is received at itsother end within the tubular socket H of head casting A.

A tube 32 connects the tubular extension l3 of casting A with thetubular extension 20 of casting C.

With the construction shown, it that casting D is curved upwardly at itsforward end so as to receive straight tube 3|. The casting is thencurved almost to a horizontal plane so that the collar 25 is in completealignment with the tube It. sharply downwardly to rest upon theextension 22 of casting C, the collar 25 of casting D centering thebrace-arm 26 so that it remains always in true alignment with casting C.

As stated above, I prefer to form the castings of aluminum alloy, suchas, for example, duralumin. Preferably, the tubes are also formed ofthis material, although other suitable metals may be used. The use ofaluminum or aluminum alloys has been considered impractical heretoforefor this purpose owing to the comparatively low tensile strength ofaluminum or aluminum alloys. To gain the proper strength, castings ofother metals would be too heavy and unwieldly. Aluminum alloys, such asduralumin can be heat-treated to give them a tensile strength comparableto steel, with the weight only one-third of a similar casting of steel.Should, however, the casting after being heat treated be subjected to awelding or brazing heat, the benefit from the heat treating would belost and the casting would be no stronger than ordinary commercialaluminum. It is apparent, therefore, that to preserve the strength ofthe heat treated alloy, no fusing temperature may be will be noted Thebrace 26 is then curved used. I have found that a temperature of 300 F.may be maintained for a limited time without danger or for a briefperiod, it is possible to go as high as 350 F.

I have found that a satisfactory aluminum alloy frame can be producedthrough the use of aluminum castings to which tubing is joined byshrinking the castings upon the tubing. For example, one of thecastings, say casting A, is heated, preferably in a liquid bath, to atemperature of around 300 F. so that the tubular extensions II and I3expand sufficiently to receive connecting tubes that are normally toolarge to be received within the tubular extensions. I have found that asatisfactory joint can be made by having the tubes from 1 1000th t1000ths larger than the bore of the tubular extensions.

By the above method, I have connected the head casting A to the tubes 3!and 32, the cluster casting B to the tube iii, the hanger casting C tothe tubes l6 and 32, and the brace-casting D to the lower end of tube35.

An extremely sturdy connection may be formed through the expansion ofthe casting by heat and the subsequent contraction thereof about a tubewhich is several thousandths greater in diameter than the diameter ofthe bore in the casting. Additional strength for the connection can beobtained by chilling the tube while at the same time heating thecasting. When the chilled tube is placed within the expanded bore of thecasting, a substantial shrinking of the bore and expansion of the tubeoccurs which produces a very tight fit.

In order to facilitate securing an effective shrunk fit, an aluminumalloy having a high lineal coefiicient of thermal expansion is used.Duralumin, for example, has a coefficient about two and one-half timesthat of ordinary cast iron, and slightly more than double that of steel.To secure a strong connection if iron were used for the castings in abicycle frame, it would be necessary to hold the internal diameter ofthe opening in the casting and the external diameter of the tube withinlimits of less than a thousandth of an inch, limits not economicallypracticable in bicycle manufacture. The alloy used, on the other hand,permits manufacturing limits several times those possible with castiron, due to its higher coefficient of expansion, and has a tensilestrength, when properly treated, comparable to that of steel.

The resultant frame is light in weight, devoid of objectionable weldingmarks, screw and bolt connections, and is sturdy and substantiallyintegral in construction.

While I have described the castings as being secured to the tubes byshrinking the castings thereon, it will be understood that, if desired,the tubes may be expanded within the castings or both methods may beused simultaneously; and in using the words shrunk fit in the appendedclaims, I intend to cover either or both methods. It will also beunderstood that my invention may be employed by forcing one of the tubeswithin the tubular extensions of a casting. Such a force fit may besupplemented by passing pins or other connecting means through thetelescoping parts.

With respect to the brace-casting D, and its connections with the frame,I have found that this construction is not only desirable with analuminum alloy frame, but also very satisfactory with steel frames orframes of other metals, and I do not desire to be limited in theappended claims to aluminum metal alloys.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, but the appended claims should be construed as broadly aspermissible, in View of the prior art.

I claim:

7 1. In a bicycle frame of the character set forth, a head member, ahanger member equipped with a rear extension, a cluster member, a tubeconnecting the cluster and hanger members, and a tube extendingdownwardly from the top portion of the head member and resting on saidhanger member extension, said last-mentioned tube being equipped with atransverse collar receiving said first-mentioned tube.

2. In a bicycle frame of the character set forth, a head member, ahanger member equipped with a rear extension, a cluster member, a tubeconnecting the cluster and hanger members, a brace-member equipped witha collar receiving said first-mentioned tube and with a brace-armresting on said hanger member extension, said brace member being alsoprovided with a forward tubular extension, a tube connecting saidtubular extension with the top portion of said head member, and a secondtube connecting said head and said hanger members.

3. In a bicycle frame of the character set forth, a head casting, ahanger casting equipped with a rear extension, a cluster casting, a tubeconnecting the cluster and hanger castings, and a tube extendingdownwardly from the top portion of said head casting and resting on saidhanger casting extension, said last mentioned tube being equipped with atransverse collar receiving said first mentioned tube.

4. In a bicycle frame of the character set forth, a head casting, ahanger casting, a cluster casting, a tube connecting the cluster andhanger castings, a brace-casting provided with a transverse openingreceiving said tube and having a downwardly curved brace resting on saidhanger casting, and a tube connecting said brace-casting to a topportion of said head casting.

5. In a bicycle frame of the character set forth, a head casting, acluster casting, a hanger casting equipped with a rear extension, a tubeconnecting the cluster and hanger castings, a curved brace-castinghaving a substantially horizontal central portion provided with atransverse collar receiving said tube and having also a downwardlyextending brace arm resting on said hanger casting extension, and a tubeconnecting said brace-casting to the top portion of said head casting.

6. In a bicycle frame of the character set forth, a head casting, ahanger casting, and a cluster casting, said hanger casting beingprovided with a rear extension, a tube connecting the cluster and hangercastings, a substantially S-shaped brace-casting provided with atransverse opening receiving said tube, the lower end portion of saidbrace-casting resting on said hanger casting extension, and a straighttube connecting the forward end of said brace-casting with said headcasting.

GEORGE S. LEWIS.

